Subclass Asteridaetakhtajan 1966

The subclass Asteridae is the most advanced subclass of Dicotyledons. It consists of 11 orders, 49 families, and nearly 60000 species of plants believed to have originated through development from or near to the order Rosales during the Tertiary period (Appendix I). In terms of the number of species, the subclass Asteridae is about the same size as that of the subclass Rosidae, but in terms of the number of families, it is surpassed by those of both the subclass Rosidae and subclass Dilleniidae. Approximately a third of the species belong to the very successful family Asteraceae, which is the largest and most evolved family of the class Magnoliopsida, and one of the two largest families of the division Magnoliophyta. The general botanical tendency observed in Asteridae is a fusion of sepals, petals and carpels into tubular perianth and single ovaries. The chemical weapons used in this Subclass are mostly monoterpenoid indole alkaloids, pyrrolizidine alkaloids, iridoid glycosides, phenylethanoid glycosides, cardiotoxic glycosides, naphthoquinones, diterpenes, sesquiterpenes and acetylene fatty acids. The order Gentianales is primitive in the Asteridae and is a common ancestor for the Rubiales, Dipsacales and Asterales (Appendix I).

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